Disposable test strips provided with apertures have been used for analysis of biological fluids such as blood, urine and saliva, and for analyzing rinse water of medical equipment for the residual level of disinfecting or sanitizing agents such as chlorine. As illustrated by U.S. Pat. No. 6,541,269 to Ramana et al. and U.S. Pat. No. 5,498,547 to Blake et al., apertured test strips have also been used for pool, spa and tap water analysis.
In a typical analysis using a reflectometer, the reflectometer includes one or more light sources for emitting light at one or more selected wavelengths, an object being analyzed reflects a portion of the emitted light, and one or more reflectometer detectors or sensors is positioned to receive the reflected light. A processor analyzes the reflected light information and provides a test result.
When as illustrated by U.S. Pat. No. 6,518,034 to Phillips et al., an apertured test strip is used with a reflectometer, the test strip is inserted into the reflectometer so that the test strip aperture is in registration with a reflectometer light source. However, test strip insertion into a reflectometer allows potentially interfering or contaminating materials such as liquid drops and dirt and debris, to contaminate the reflectometer optics. In addition, positioning of a reacted test strip pad with respect to the reflectometer light source, may vary or the test strip pad may move during analysis, so as to produce inconsistent or inaccurate results.
A reflectometry apparatus illustrated by U.S. Patent Application No. 2008/0113398 to Lin et al., includes a foldable test strip holder that when open, provides a groove into which a test strip including an enzyme pad spaced apart from a color indicator pad, is placed. The test strip holder is provided with an aperture, and when closed, the opaque pads contact one another and the opaque, reacted color indicator pad may be viewed through the test strip holder aperture and the transparent support of the test strip. The exterior of the test strip holder and interior of the reflectometer provide a mating fit of the test strip holder within the reflectometer. However, that apparatus appears to have limited analytical applicability. For example, it requires an enzyme pad, addition of sample to the enzyme pad, and physical contact of the test strip pads with each other.
Despite improvements in colorimetric analysis, there continues to be a need for consistency of results and improved sensitivity.